The present invention relates to high strength insulating refractory shapes and particularly brick suitable for use as backup brick in metallurgical vessels and working face linings for rotary kilns.
Typically such brick as now commonly used contain at least one lightweight aggregate to increase porosity and insulating properties and are manufactured by a variety of processes including the conventional mixing and pressing procedures used to make brick and are burned in periodic or tunnel kilns. Aggregates used for this purpose include, for example, bubble alumina, perlite, diatomite, and expanded clay, shale or other expanded mineral aggregates.
However, such aggregates have not proven satisfactory since the resultant brick lack the high strength required as well as the high insulating properties desired. Equally important, such aggregates make it difficult to produce brick of substantially uniform size, weight, and density resulting in difficulties in making satisfactory vessel linings using such brick.
Due to segregation and breakdown of such aggregates because of their lighter weight in the mix and low strength, there is inconsistent brick-to-brick weight and density. Also, because of the low refractoriness of most such lightweight aggregates as well as their nonuniformity there often occurs significant variation in size of the brick after firing due to inconsistent linear burning change and squeezing of the brick when stacked in kiln cars. Efforts to overcome these problems have not been successful.